What are enantiomers in coordination compounds?

In coordination compounds, enantiomers are a type of optical isomer—molecules that are non-superimposable mirror images of each other. They have the same composition and connectivity but differ in the spatial arrangement of ligands around the central metal ion in such a way that they cannot be placed on top of each other exactly.

Here’s a simple breakdown:

1. Chirality in Coordination Compounds:
   • A complex is chiral if it lacks a plane of symmetry.
   • The central metal with its attached ligands forms a “handed” arrangement—like left and right hands.
2. Common Examples:
   • Octahedral complexes with three bidentate ligands (like [Co(en)₃]³⁺) often show enantiomerism.
     • Two forms: Δ (delta) → right-handed twist,
     • Λ (lambda) → left-handed twist.
   • These two forms are mirror images but cannot be superimposed.
3. Properties of Enantiomers:
   • Chemically similar in an achiral environment.
   • Rotate plane-polarized light in opposite directions (one is dextrorotatory, the other levorotatory).
   • Can react differently with other chiral molecules (important in bioinorganic chemistry).

In short: Enantiomers in coordination compounds are mirror-image forms of a complex that are chiral, giving rise to optical activity.